Nucleotide sequences which code for the cysD, cysN, cysK, cysE and cysH genes

ABSTRACT

Nucleotide sequences from coryneform bacteria which code for the cysD, cysN, cysK, cysE and cysH genes and a process for the fermentative preparation of amino acids using bacteria in which the genes mentioned are enhanced, a process for the fermentative preparation of L-amino acids using coryneform bacteria in which at least the cysD gene, the cysN gene, the cysK gene, the cysE gene and/or the cysH gene is present in enhanced form, and the use of polynucleotides which contain the sequences according to the invention as hybridization probes and a process for the preparation of an L-methionine-containing animal feedstuffs additive from fermentation broths.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit to U.S. Provisional Application Ser. No. 60/294,223, filed on May 31, 2001 and incorporated herein by reference.

FIELD OF THE INVENTION

The present invention provides nucleotide sequences from coryneform bacteria which code for the cysD, cysN, cysK, cysE and cysH genes and a process for the fermentative preparation of amino acids using bacteria in which the endogene genes mentioned are enhanced.

DESCRIPTION OF THE BACKGROUND

L-Amino acids, in particular L-lysine, L-cysteine and L-methionine, are used in human medicine and in the pharmaceuticals industry, in the foodstuffs industry and very particularly in animal nutrition.

It is known that amino acids are prepared by fermentation from strains of coryneform bacteria, in particular Corynebacterium glutamicum. Because of their great importance, work is constantly being undertaken to improve the preparation processes. Improvements to the process can relate to fermentation procedures, such as, for example, stirring and supply of oxygen, or the composition of the nutrient media, such as, for example, the sugar concentration during the fermentation, or the working up to the product form by, for example, ion exchange chromatography, or the intrinsic output properties of the microorganism itself.

Methods of mutagenesis, selection and mutant selection are used to improve the output properties of these microorganisms. Strains which are resistant to antimetabolites or are auxotrophic for metabolites of regulatory importance and produce amino acids are obtained in this manner.

Methods of the recombinant DNA technique have also been employed for some years for improving the strain of Corynebacterium strains which produce L-amino acid, by amplifying individual amino acid biosynthesis genes and investigating the effect on the amino acid production.

However, there remains a need for improved methods of producing amino acids.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide new methods for improved fermentative preparation of amino acids.

It is another object of the invention to provide nucleic acids which are useful for preparing amino acids.

Accordingly, the present invention provides isolated polynucleotides from coryneform bacteria comprising one or more of the polynucleotide sequences which code for the cysD gene, the cysN gene, the cysK gene, the cysE gene or the cysH gene, selected from the group consisting of

-   -   (a) polynucleotide which is identical to the extent of at least         70% to a polynucleotide which codes for a polypeptide which         comprises the amino acid sequence of SEQ ID No. 2,     -   (b) polynucleotide which is identical to the extent of at least         70% to a polynucleotide which codes for a polypeptide which         comprises the amino acid sequence of SEQ ID No. 3,     -   (c) polynucleotide which is identical to the extent of at least         70% to a polynucleotide which codes for a polypeptide which         comprises the amino acid sequence of SEQ ID No. 5,     -   (d) polynucleotide which is identical to the extent of at least         70% to a polynucleotide which codes for a polypeptide which         comprises the amino acid sequence of SEQ ID No. 6,     -   (e) polynucleotide which is identical to the extent of at least         70% to a polynucleotide which codes for a polypeptide which         comprises the amino acid sequence of SEQ ID No. 8,     -   (f) polynucleotide which codes for a polypeptide which comprises         an amino acid sequence which is identical to the extent of at         least 70% to the amino acid sequence of SEQ ID No. 2,     -   (g) polynucleotide which codes for a polypeptide which comprises         an amino acid sequence which is identical to the extent of at         least 70% to the amino acid sequence of SEQ ID No. 3,     -   (h) polynucleotide which codes for a polypeptide which comprises         an amino acid sequence which is identical to the extent of at         least 70% to the amino acid sequence of SEQ ID No. 5,     -   (i) polynucleotide which codes for a polypeptide which comprises         an amino acid sequence which is identical to the extent of at         least 70% to the amino acid sequence of SEQ ID No. 6,     -   (j) polynucleotide which codes for a polypeptide which comprises         an amino acid sequence which is identical to the extent of at         least 70% to the amino acid sequence of SEQ ID No. 8,     -   (k) polynucleotide which is complementary to the polynucleotides         of (a), (b), (c), (d), (e), (f), (g), (h), (i) or (j), and     -   (l) polynucleotide comprising at least 15 successive nucleotides         of the polynucleotide sequence of (a), (b), (c), (d), (e), (f),         (g), (h), (i), (j) or (k),     -   where the polypeptides preferably having the corresponding         activities, namely of sulfate adenylyl transferase, cysteine         synthase A, serine acetyl transferase or 3′-phosphoadenylyl         sulfate reductase.

The present invention also provides the above-mentioned polynucleotides, these preferably being DNAs which are capable of replication, comprising:

-   -   (i) one or more nucleotide sequences shown in SEQ ID No. 1, SEQ         ID No. 4 or SEQ ID No. 7, or     -   (ii) at least one sequence which corresponds to sequence (i)         within the range of the degeneration of the genetic code, or     -   (iii) at least one sequence which hybridizes with the sequence         complementary to sequence (i) or (ii), and optionally     -   (iv) sense mutations of neutral function in (i).

The present invention also provides polynucleotides, in particular DNAs, which are capable of replication and comprise one or more nucleotide sequences as shown in SEQ ID No. 1, SEQ ID No.4, or SEQ ID No. 7;

-   -   polynucleotides which code for one or more polypeptides which         comprises the corresponding amino acid sequences, as shown in         SEQ ID No. 2, SEQ ID No. 3, SEQ ID No. 5, SEQ ID No. 6, or SEQ         ID No. 8;     -   a vector containing one or more of the polynucleotides according         to the invention, in particular shuttle vectors or plasmid         vectors, and     -   coryneform bacteria which contain the vector or in which one or         more of the endogene genes chosen from the group consisting of         the cysD gene, cysN gene, cysK gene, cysE gene and cysH gene         is/are enhanced.

The present invention additionally provides a process for the fermentative preparation of amino acids using bacteria in which one or more endogene genes chosen from the group consisting of

-   -   the cysD gene which codes for the subunit II of sulfate         adenylyltransferase,     -   the cysN gene which codes for the subunit I of sulfate adenylyl         transferase,     -   the cysK gene which codes for cysteine synthase A,     -   the cysE gene which codes for serine acetyl transferase,     -   the cysH gene which codes for 3′-phosphoadenylyl sulfate         reductase is enhanced.

All five endogene genes (cysD gene, cysN gene, cysK gene, cysE gene and cysH gene) participate in the biosynthesis of the sulfur-containing L-amino acids L-cysteine and L-methionine. The carbon matrix of these amino acids is predominantly derived from the same metabolic intermediates as that of the amino acids of the aspartate family, to which L-lysine belongs. Over-expression of one or more of the genes mentioned leads to pool shifts in the participating biosynthesis pathways, which has a positive effect on the formation of L-lysine, L-methionine and L-cysteine.

The present invention also provides a process for the fermentative preparation of an L-amino acid comprising:

-   -   (a) fermenting coryneform bacteria in a medium, wherein the         bacteria produce the desired L-amino acid and in which at least         the cysD gene, cysN gene, cysK gene, cysE gene and/or the cysH         gene or nucleotide sequences which code for them is or are         enhanced.     -   (b) concentrating the L-amino acid in the medium or in the cells         of the bacteria, and     -   (c) isolating the L-amino acid.

The present invention further provides a process of the preparation of an L-methionine-containing animal feedstuffs additive from a fermentation broth, comprising:

-   -   (a) culturing and fermenting an L-methionine-producing         microorganism in a fermentation medium;     -   (b) removing water from the L-methionine-containing fermentation         broth;     -   (c) removing an amount of from 0 to 100 wt. % of the biomass         formed during the fermentation; and     -   (d) drying he fermentation broth obtained according to (b)         and/or (c) to obtain the animal feedstuffs additive in powder or         granule form.

The present invention additionally provides A process of isolating nucleic acids, or polynucleotides or genes, such as RNA, cDNA, or DNA, which code for sulfate adenylyl transferase, cysteine synthase A, serine acetyl transferase and/or 3′-phosphoadenylyl sulfate reductase or have a high similarity with the sequences of the cysD gene, the cysN gene, the cysK gene, the cysE gene and/or the cysH gene, comprising:

-   -   contacting a sample with the polynucleotide described above         under conditions such that the polynucleotide is capable of         hybridizing to another polynucleotide which codes for sulfate         adenylyl transferase, cysteine synthase A, serine acetyl         transferase and/or 3′-phosphoadenylyl sulfate reductase or have         a high similarity with the sequences of the cysD gene, the cysN         gene, the cysK gene, the cysE gene and/or the cysH gene.

The invention also provides polynucleotides which substantially comprise a polynucleotide sequence, which are obtainable by screening by means of hybridization of a corresponding gene library of a coryneform bacterium, which comprises the complete gene or parts thereof, with a probe which comprises the sequence of the polynucleotides according to the invention according to SEQ ID No. 1, SEQ ID No. 4 or SEQ ID No. 7 or a fragment thereof, and isolation of the polynucleotide sequence mentioned.

BRIEF DESCRIPTION OF THE FIGURES

A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

FIG. 1: Map of the plasmid pEC-XK99E.

FIG. 2: Map of the plasmid pEC-XK99EcysDa1ex.

FIG. 3: Map of the plasmid pEC-XK99EcysKa1ex.

FIG. 4: Map of the plasmid pEC-XK99EcysEb1ex.

FIG. 5: Map of the plasmid pEC-XK99EcysHa1ex.

DETAILED DESCRIPTION OF THE INVENTION

The abbreviations and designations used herein have the following meaning:

-   -   Kan: Kanamycin resistance gene aph(3′)-IIa from Escherichia coli     -   HindIII: Cleavage site of the restriction enzyme HindIII     -   XbaI: Cleavage site of the restriction enzyme XbaI     -   KpnI: Cleavage site of the restriction enzyme KpnI     -   Ptrc: trc promoter     -   T1: Termination region T1     -   T2: Termination region T2     -   per: Replication effector per     -   rep: Replication region rep of the plasmid pGA1     -   lacIq: lacIq repressor of the lac operon of Escherichia coli     -   cysD: Cloned cysD gene     -   cysK: Cloned cysK gene     -   cysE: Cloned cysE gene     -   cysH: Cloned cysH gene

Where L-amino acids or amino acids are mentioned herein, refers to one or more amino acids, including their salts, chosen from the group consisting of L-asparagine, L-threonine, L-serine, L-glutamate, L-glycine, L-alanine, L-cysteine, L-valine, L-methionine, L-isoleucine, L-leucine, L-tyrosine, L-phenylalanine, L-histidine, L-lysine, L-tryptophan and L-arginine. L-Lysine and the sulfur-containing L-amino acids L-cysteine and L-methionine are particularly preferred.

The terms “L-lysine” or “lysine” refer not only the bases but also the salts, such as e.g. lysine monohydrochloride or lysine sulfate.

The terms “L-cysteine” or “cysteine” refer also to the salts, such as e.g. cysteine hydrochloride or cysteine S-sulfate, of this amino acid.

The terms “L-methionine” or “methionine” also include the salts, such as e.g. methionine hydrochloride or methionine sulfate, of this amino acid.

Polynucleotides which comprise the sequences according to the invention are suitable as hybridization probes for RNA, cDNA and DNA, in order to isolate, in the full length, nucleic acids or polynucleotides or genes which code for sulfate adenylyl transferase, cysteine synthase A, serine acetyl transferase and/or 3′-phosphoadenylyl sulfate reductase, or to isolate those nucleic acids or polynucleotides or genes which have a high similarity of sequence with that of the cysD gene, the cysN gene, the cysK gene, the cysE gene and/or the cysH gene.

Polynucleotides which comprise the sequences according to the invention are furthermore suitable as primers with the aid of which DNA of genes which code for sulfate adenylyl transferase, cysteine synthase A, serine acetyl transferase and/or 3′-phosphoadenylyl sulfate reductase can be prepared by the polymerase chain reaction (PCR).

In one aspect of this invention, the cysD gene according to the invention codes for the subunit II of sulfate adenylyl transferase, the cysN gene according to the invention codes for the subunit I of sulfate adenylyl transferase, the cysK gene according to the invention codes for cysteine synthase A, the cysE gene according to the invention codes for serine acetyl transferase and the cysH gene according to the invention codes for 3′-phosphoadenylyl sulfate reductase.

In another aspect of this invention, it is possible that these genes according to the invention occur in pairs or in combination with several genes, in which case they then code for the combined activities. That is to say, if, for example, the a) cysE gene and cysK gene, or b) cysK gene and cysH gene, or c) cysN gene and cysD gene and cysE gene and cysK gene are enhanced at the same time, these code for a) serine acetyl transferase and cysteine synthase A, b) cysteine synthase A and 3′-phosphoadenylyl sulfate reductase, and c) sulfate adenylyl transferase and serine acetyltransferase and cysteine synthase A.

Such oligonucleotides which serve as probes or primers comprise at least 30, preferably at least 20, very particularly preferably at least 15 successive nucleotides. Oligonucleotides which have a length of at least 40 or 50 nucleotides are also suitable. Oligonucleotides with a length of at least 100, 150, 200, 250 or 300 nucleotides are optionally also suitable.

The term “isolated” refers to a material separated out of its natural environment.

The term “polynucleotide” in general refers to polyribonucleotides and polydeoxyribonucleotides. It being possible for these to be non-modified RNA or DNA or modified RNA or DNA.

The polynucleotides according to the invention include a polynucleotide according to SEQ ID No. 1, SEQ ID No. 4, or SEQ ID No. 7 or a fragment prepared therefrom and also those which are at least 70%, preferably at least 80% and in particular at least 90% to 95% identical to the polynucleotide according to SEQ ID No. 1, SEQ ID No.4 or SEQ ID No. 7 or a fragment prepared therefrom.

The term “polypeptides” refers to peptides or proteins which comprise two or more amino acids bonded via peptide bonds.

The polypeptides according to the invention include the polypeptides according to SEQ ID No. 2, SEQ ID No. 3, SEQ ID No. 5, SEQ ID No. 6 and SEQ ID No. 8, in particular those with the biological activity of sulfate adenylyl transferase, cysteine synthase A, serine acetyl transferase and/or 3′-phosphoadenylyl sulfate reductase, and also those which are at least 70%, preferably at least 80% and in particular at least 90% to 95% identical to the polypeptides according to SEQ ID No. 2, SEQ ID No. 3, SEQ ID No. 5, SEQ ID No. 6 or SEQ ID No. 8 and have the activities mentioned.

The invention furthermore relates to a process for the fermentative preparation of amino acids chosen from the group consisting of L-asparagine, L-threonine, L-serine, L-glutamate, L-glycine, L-alanine, L-cysteine, L-valine, L-methionine, L-isoleucine, L-leucine, L-tyrosine, L-phenylalanine, L-histidine, L-lysine, L-tryptophan and L-arginine using coryneform bacteria which in particular already produce amino acids and in which the nucleotide sequences which code for the cysD gene, the cysN gene, cysE gene, the cysK gene and/or the cysH gene are enhanced, in particular over-expressed.

The term “enhancement” in this respect describes the increase in the intracellular activity of one or more enzymes (proteins) in a microorganism which are coded by the corresponding DNA, for example by increasing the number of copies of the gene or genes, using a potent promoter or using a gene or allele which codes for a corresponding enzyme (protein) having a high activity, and optionally combining these measures.

By enhancement measures, in particular over-expression, the activity or concentration of the corresponding protein is in general increased by at least 10%, 25%, 50%, 75%, 100%, 150%, 200%, 300%, 400% or 500%, up to a maximum of 1000% or 2000%, based on that of the wild-type protein or the activity or concentration of the protein in the starting microorganism.

The microorganisms which the present invention provides can produce L-amino acids from glucose, sucrose, lactose, fructose, maltose, molasses, starch, cellulose or from glycerol and ethanol. They can be representatives of coryneform bacteria, in particular of the genus Corynebacterium. Of the genus Corynebacterium, there may be mentioned in particular the species Corynebacterium glutamicum, which is known by those skilled in the art for its ability to produce L-amino acids.

Suitable strains of the genus Corynebacterium, in particular of the species Corynebacterium glutamicum (C. glutamicum), are in particular the known wild-type strains

-   -   Corynebacterium glutamicum ATCC13032     -   Corynebacterium acetoglutamicum ATCC 15806     -   Corynebacterium acetoacidophilum ATCC 13870     -   Corynebacterium thermoaminogenes FERM BP-1539     -   Corynebacterium melassecola ATCC17965     -   Brevibacterium flavum ATCC 14067     -   Brevibacterium lactofermentum ATCC 13869 and     -   Brevibacterium divaricatum ATCC14020         and L-amino acid-producing mutants or strains prepared         therefrom.

The new cysD, cysN, cysK, cysE and cysH genes of C. glutamicum which code for the enzymes sulfate adenylyl transferase (EC 2.7.7.4), cysteine synthase A (EC 4.2.99.8), serine acetyl transferase (EC 2.3.1.30) and 3′-phosphoadenylyl sulfate reductase (EC 1.8.99.4) have been isolated.

To isolate the cysD gene, the cysN gene, the cysK gene, the cysE gene, the cysH gene or also other genes of C. glutamicum, a gene library of this microorganism is first established in Escherichia coli (E. coli). The establishment of gene libraries is described in generally known textbooks and handbooks. The textbook by Winnacker: Gene und Klone, Eine Einführung in die Gentechnologie (Verlag Chemie, Weinheim, Germany, 1990), or the handbook by Sambrook et al.: Molecular Cloning, A Laboratory Manual (Cold Spring Harbor Laboratory Press, 1989) may be mentioned as an example. A well-known gene library is that of the E. coli K-12 strain W3110 set up in λ vectors by Kohara et al. (Cell 50, 495-508 (1987)). Bathe et al. (Molecular and General Genetics, 252:255-265, 1996) describe a gene library of C. glutamicum ATCC13032, which was established with the aid of the cosmid vector SuperCos I (Wahl et al., 1987, Proceedings of the National Academy of Sciences USA, 84:2160-2164) in the E. coli K-12 strain NM554 (Raleigh et al., 1988, Nucleic Acids Research 16:1563-1575).

Börmann et al. (Molecular Microbiology 6(3), 317-326) (1992)) in turn describe a gene library of C. glutamicum ATCC 13032 using the cosmid pHC79 (Hohn and Collins, Gene 11, 291-298 (1980)).

To prepare a gene library of C. glutamicum in E. coli it is also possible to use plasmids such as pBR322 (Bolivar, Life Sciences, 25, 807-818 (1979)) or pUC9 (Vieira et al., 1982, Gene, 19:259-268). Suitable hosts are, in particular, those E. coli strains which are restriction- and recombination-defective. An example of these is the strain DH5αmcr, which has been described by Grant et al. (Proceedings of the National Academy of Sciences USA, 87 (1990) 4645-4649). The long DNA fragments cloned with the aid of cosmids can in turn be subcloned in the usual vectors suitable for sequencing and then sequenced, as is described e.g. by Sanger et al. (Proceedings of the National Academy of Sciences of the United States of America, 74:5463-5467, 1977).

The resulting DNA sequences can then be analyzed with known algorithms or sequence analysis programs, such as e.g. that of Staden (Nucleic Acids Research 14, 217-232(1986)), that of Marck (Nucleic Acids Research 16, 1829-1836 (1988)) or the GCG program of Butler (Methods of Biochemical Analysis 39, 74-97 (1998)).

The new DNA sequences of C. glutamicum which code for the cysD, cysN, cysK, cysE and cysH genes and which, as SEQ ID No. 1, SEQ ID No. 4, and SEQ ID No. 7, are constituents of the present invention have been found. The amino acid sequence of the corresponding proteins has furthermore been derived from the present DNA sequences by the methods described above. The resulting amino acid sequences of the cysD, cysN, cysK, cysE and cysH gene products are shown in SEQ ID No. 2, SEQ ID No. 3, SEQ ID No. 5, SEQ ID No. 6, and SEQ ID No. 8.

Coding DNA sequences which result from SEQ ID No. 1, SEQ ID No. 4 or SEQ ID No. 7 by the degeneracy of the genetic code are also a constituent of the invention. In the same way, DNA sequences which hybridize with SEQ ID No. 1 or parts of SEQ ID No. 1 or SEQ ID No. 4 or parts of SEQ ID No. 4 or SEQ ID No. 7 or parts of SEQ ID No. 7 are a constituent of the invention. Conservative amino acid exchanges, such as e.g. exchange of glycine for alanine or of aspartic acid for glutamic acid in proteins, are furthermore known in the art as “sense mutations” which do not lead to a fundamental change in the activity of the protein, i.e. are of neutral function. It is furthermore known that changes on the N and/or C terminus of a protein cannot substantially impair or can even stabilize the function thereof. Information in this context can be found by those skilled in the art, inter alia, in Ben-Bassat et al. (Journal of Bacteriology 169:751-757 (1987)), in O'Regan et al. (Gene 77:237-251 (1989)), in Sahin-Toth et al. (Protein Sciences 3:240-247 (1994)), in Hochuli et al. (Bio/Technology 6:1321-1325 (1988)) and in known textbooks of genetics and molecular biology. Amino acid sequences which result in a corresponding manner from SEQ ID No. 2, SEQ ID No. 3, SEQ ID No. 5, SEQ ID No. 6 and SEQ ID No. 8 are within the scope of the present invention.

In the same way, DNA sequences which hybridize with SEQ ID No. 1 or parts of SEQ ID No. 1 or SEQ ID No. 4 or parts of SEQ ID No. 4 or SEQ ID No. 7 or parts of SEQ ID No. 7 are a constituent of the invention. Finally, DNA sequences which are prepared by the polymerase chain reaction (PCR) using primers which result from SEQ ID No. 1, SEQ ID No. 4 or SEQ ID No. 7 are a constituent of the invention. Such oligonucleotides typically have a length of at least 15 nucleotides.

Instructions for identifying DNA sequences by means of hybridization, inter alia, in the handbook “The DIG System Users Guide for Filter Hybridization” from Boehringer Mannheim GmbH (Mannheim, Germany, 1993) and in Liebl et al. (International Journal of Systematic Bacteriology (1991) 41: 255-260). The hybridization takes place under stringent conditions, that is to say only hybrids in which the probe and target sequence, i. e. the polynucleotides treated with the probe, are at least 70% identical are formed. It is known that the stringency of the hybridization, including the washing steps, is influenced or determined by varying the buffer composition, the temperature and the salt concentration. The hybridization reaction is preferably carried out under a relatively low stringency compared with the washing steps (Hybaid Hybridisation Guide, Hybaid Limited, Teddington, UK, 1996).

A 5×SSC buffer at a temperature of approx. 50° C.-68° C., for example, can be employed for the hybridization reaction. Probes can also hybridize here with polynucleotides which are less than 70% identical to the sequence of the probe. Such hybrids are less stable and are removed by washing under stringent conditions. This can be achieved, for example, by lowering the salt concentration to 2×SSC and optionally subsequently 0.5×SSC (The DIG System User's Guide for Filter Hybridisation, Boehringer Mannheim, Mannheim, Germany, 1995) a temperature of approx. 50° C.-68° C. being established. It is optionally possible to lower the salt concentration to 0.1×SSC. Polynucleotide fragments which are, for example, at least 70% or at least 80% or at least 90% to 95% identical to the sequence of the probe employed can be isolated by increasing the hybridization temperature stepwise from 50° C. to 68° C. in steps of approx. 1-2° C. Further instructions on hybridization are obtainable on the market in the form of so-called kits (e.g. DIG Easy Hyb from Roche Diagnostics GmbH, Mannheim, Germany, Catalogue No. 1603558).

Instructions for amplification of DNA sequences with the aid of the polymerase chain reaction (PCR) can be found inter alia, in the handbook by Gait: Oligonucleotide Synthesis: A Practical Approach (IRL Press, Oxford, UK, 1984) and in Newton and Graham: PCR (Spektrum Akademischer Verlag, Heidelberg, Germany, 1994).

It has been found that coryneform bacteria produce amino acids in an improved manner after over-expression of one or more of the genes chosen from the group consisting of the cysD gene, cysN gene, cysK gene, cysE gene and cysH gene.

To achieve an over-expression, the number of copies of the corresponding genes can be increased, or the promoter and regulation region or the ribosome binding site upstream of the structural gene can be mutated. Expression cassettes which are incorporated upstream of the structural gene act in the same way. By inducible promoters, it is additionally possible to increase the expression in the course of fermentative amino acid production. The expression is likewise improved by measures to prolong the life of the m-RNA. Furthermore, the enzyme activity is also increased by preventing the degradation of the enzyme protein. The genes or gene constructs can either be present in plasmids with a varying number of copies, or can be integrated and amplified in the chromosome. Alternatively, an over-expression of the genes in question can furthermore be achieved by changing the composition of the media and the culture procedure.

Instructions in this context can be found by those skilled in the art, inter alia, in Martin et al. (Bio/Technology 5, 137-146 (1987)), in Guerrero et al. (Gene 138, 35-41 (1994)), Tsuchiya and Morinaga (Bio/Technology 6, 428-430 (1988)), in Eikmanns et al. (Gene 102, 93-98 (1991)), in EP 0 472 869, in U.S. Pat. No. 4,601,893, in Schwarzer and Pühler (Bio/Technology 9, 84-87 (1991), in Reinscheid et al. (Applied and Environmental Microbiology 60, 126-132 (1994)), in LaBarre et al. (Journal of Bacteriology 175, 1001-1007 (1993)), in WO 96/15246, in Malumbres et al. (Gene 134, 15-24 (1993)), in JP-A-10-229891, in Jensen and Hammer (Biotechnology and Bioengineering 58, 191-195 (1998)), in Makrides (Microbiological Reviews 60:512-538 (1996)) and in known textbooks of genetics and molecular biology.

By way of example, for enhancement the cysD, cysN, cysK, cysE or cysH genes according to the invention were over-expressed with the aid of episomal plasmids. Suitable plasmids are those which are replicated in coryneform bacteria. Numerous known plasmid vectors, such as e.g. pZ1 (Menkel et al., Applied and Environmental Microbiology (1989) 64: 549-554), pEKEx1 (Eikmanns et al., Gene 102:93-98 (1991)) or pHS2-1 (Sonnen et al., Gene 107:69-74 (1991)) are based on the cryptic plasmids pHM1519, pBL1 or pGA1. Other plasmid vectors, such as e.g. those based on pCG4 (U.S. Pat. No. 4,489,160), or pNG2 (Serwold-Davis et al., FEMS Microbiology Letters 66, 119-124 (1990)), or pAG1 (U.S. Pat. No. 5,158,891), can be used in the same manner.

Plasmid vectors which are furthermore suitable are also those with the aid of which the process of gene amplification by integration into the chromosome can be used, as has been described, for example, by Reinscheid et al. (Applied and Environmental Microbiology 60, 126-132 (1994)) for duplication or amplification of the hom-thrB operon. In this method, the complete gene is cloned in a plasmid vector which can replicate in a host (typically E. coli), but not in C. glutamicum. Possible vectors are, for example, pSUP301 (Simon et al., Bio/Technology 1, 784-791 (1983)), pK18mob or pK19mob (Schafer et al., Gene 145, 69-73 (1994)), pGEM-T (Promega Corporation, Madison, Wis., USA), pCR2.1-TOPO (Shuman (1994). Journal of Biological Chemistry 269:32678-84; US-A 5,487,993), pCR®Blunt (Invitrogen, Groningen, Holland; Bernard et al., Journal of Molecular Biology, 234: 534-541 (1993)), pEM1 (Schrumpfet al, 1991, Journal of Bacteriology 173:4510-4516) or pBGS8 (Spratt et al.,1986, Gene 41: 337-342). The plasmid vector which contains the gene to be amplified is then transferred into the desired strain of C. glutamicum by conjugation or transformation. The method of conjugation is described, for example, by Schafer et al. (Applied and Environmental Microbiology 60, 756-759 (1994)). Methods for transformation are described, for example, by Thierbach et al. (Applied Microbiology and Biotechnology 29, 356-362 (1988)), Dunican and Shivnan (Bio/Technology 7, 1067-1070 (1989)) and Tauch et al. (FEMS Microbiological Letters 123, 343-347 (1994)). After homologous recombination by means of a “cross over” event, the resulting strain contains at least two copies of the gene in question.

In addition, it may be advantageous for the production of L-amino acids to enhance, in particular over-express, one or more enzymes of the particular biosynthesis pathway, of glycolysis, of anaplerosis, of the citric acid cycle, of the pentose phosphate cycle, of amino acid export and optionally regulatory proteins, in addition to the cysD gene, the cysN gene, the cysK gene, the cysE gene and/or the cysH gene.

Thus, for the preparation of L-amino acids, in addition to enhancement of the cysD gene, the cysN gene, the cysK gene, the cysE gene and/or the cysh gene, one or more endogene genes chosen from the group consisting of

-   -   the dapA gene which codes for dihydrodipicolinate synthase (EP-B         0 197 335),     -   the gap gene which codes for glyceraldehyde 3-phosphate         dehydrogenase (Eikmanns (1992), Journal of Bacteriology         174:6076-6086),     -   the tpi gene which codes for triose phosphate isomerase         (Eikmanns (1992), Journal of Bacteriology 174:6076-6086),     -   the pgk gene which codes for 3-phosphoglycerate kinase (Eikmanns         (1992), Journal of Bacteriology 174:6076-6086),     -   the zwf gene which codes for glucose 6-phosphate dehydrogenase         (JP-A-09224661),     -   the pyc gene which codes for pyruvate carboxylase (DE-A-198 31         609),     -   the mqo gene which codes for malate-quinone oxidoreductase         (Molenaar et al., European Journal of Biochemistry 254, 395-403         (1998)),     -   the lysC gene which codes for a feed-back resistant aspartate         kinase (Accession No.P26512; EP-B-0387527; (EP-A-0699759),     -   the lysE gene which codes for lysine export (DE-A-195 48 222),     -   the hom gene which codes for homoserine dehydrogenase (EP-A         0131171),     -   the ilvA gene which codes for threonine dehydratase (Möckel et         al., Journal of Bacteriology (1992) 8065-8072)) or the ilvA(Fbr)         allele which codes for a “feed back resistant” threonine         dehydratase (Möckel et al., (1994) Molecular Microbiology 13:         833-842),     -   the ilvBN gene which codes for acetohydroxy-acid synthase (EP-B         0356739),     -   the ilvD gene which codes for dihydroxy-acid dehydratase (Sahm         and Eggeling (1999) Applied and Environmental Microbiology 65:         1973-1979),     -   the zwa1 gene which codes for the Zwa1 protein (DE: 19959328.0,         DSM 13115) can be enhanced, in particular over-expressed.

It may furthermore be advantageous for the production of L-amino acids, in addition to enhancement of the cysD gene, the cysN gene, the cysK gene, the cysE gene and/or the cysH gene, for one or more genes chosen from the group consisting of

-   -   the pck gene which codes for phosphoenol pyruvate carboxykinase         (DE 199 50 409.1; DSM 13047),     -   the pgi gene which codes for glucose 6-phosphate isomerase (U.S.         Ser. No. 09/396,478; DSM 12969),     -   the poxB gene which codes for pyruvate oxidase (DE: 1995 1975.7;         DSM 13114),     -   the zwa2 gene which codes for the Zwa2 protein (DE: 19959327.2,         DSM 13113) to be attenuated, in particular for the expression         thereof to be reduced. For the production of L-cysteine in         particular, it may be advantageous, in addition to enhancement         of the cysD gene, the cysN gene, the cysK gene, the cysE gene         and/or the cysH gene, for one or more genes chosen from the         group consisting of     -   the aecD gene which codes for cystathionine β-lyase (Accession         Number M89931 des National Center for Biotechnology Information         (NCBI, Bethesda, Md., USA),     -   the metB gene which codes for cystathione synthase (Accession         Number AF1236953 des National Center for Biotechnology         Information (NCBI, Bethesda, Md., USA)         to be attenuated, in particular for the expression thereof to be         reduced.

The term “attenuation” in this connection describes the reduction or elimination of the intracellular activity of one or more enzymes (proteins) in a microorganism which are coded by the corresponding DNA, for example by using a weak promoter or using a gene or allele which codes for a corresponding enzyme with a low activity or inactivates the corresponding gene or enzyme (protein), and optionally combining these measures.

By attenuation measures, the activity or concentration of the corresponding protein is in general reduced to 0 to 75%, 0 to 50%, 0 to 25%, 0 to 10% or 0 to 5% of the activity or concentration of the wild-type protein or of the activity or concentration of the protein in the starting microorganism.

In addition to over-expression of the cysD gene, the cysN gene, the cysK gene, the cysE gene and/or the cysH gene it may furthermore be advantageous for the production of amino acids to eliminate undesirable side reactions (Nakayama: “Breeding of Amino Acid Producing Micro-organisms”, in: Overproduction of Microbial Products, Krumphanzl, Sikyta, Vanek (eds.), Academic Press, London, UK, 1982).

The invention also provides the microorganisms prepared according to the invention, and these can be cultured continuously or discontinuously in the batch process (batch culture) or in the fed batch (feed process) or repeated fed batch process (repetitive feed process) for the purpose of production of amino acids. A summary of known culture methods is described in the textbook by Chmiel (Bioprozesstechnik 1. Einführung in die Bioverfahrenstechnik (Gustav Fischer Verlag, Stuttgart, 1991)) or in the textbook by Storhas (Bioreaktoren und periphere Einrichtungen (Vieweg Verlag, Braunschweig/Wiesbaden, 1994)).

The culture medium to be used must meet the requirements of the particular strains in a suitable manner. Descriptions of culture media for various microorganisms are contained in the handbook “Manual of Methods for General Bacteriology” of the American Society for Bacteriology (Washington D.C., USA, 1981).

Sugars and carbohydrates, such as e.g. glucose, sucrose, lactose, fructose, maltose, molasses, starch and cellulose, oils and fats, such as e.g. soya oil, sunflower oil, groundnut oil and coconut fat, fatty acids, such as e.g. palmitic acid, stearic acid and linoleic acid, alcohols, such as e.g. glycerol and ethanol, and organic acids, such as e.g. acetic acid, can be used as the source of carbon. These substances can be used individually or as a mixture.

Organic nitrogen-containing compounds, such as peptones, yeast extract, meat extract, malt extract, corn steep liquor, soya bean flour and urea, or inorganic compounds, such as ammonium sulfate, ammonium chloride, ammonium phosphate, ammonium carbonate and ammonium nitrate, can be used as the source of nitrogen. The sources of nitrogen can be used individually or as a mixture.

Phosphoric acid, potassium dihydrogen phosphate or dipotassium hydrogen phosphate or the corresponding sodium-containing salts can be used as the source of phosphorus.

Organic and inorganic sulfur-containing compounds, such as, for example, sulfides, sulfites, sulfates and thiosulfates, can be used as a source of sulfur, in particular for the preparation of sulfur-containing amino acids.

The culture medium must furthermore comprise salts of metals, such as e. g. magnesium sulfate or iron sulfate, which are necessary for growth. Finally, essential growth substances, such as amino acids and vitamins, can be employed in addition to the above-mentioned substances. Suitable precursors can moreover be added to the culture medium. The starting substances mentioned can be added to the culture in the form of a single batch, or can be fed in during the culture in a suitable manner.

Basic compounds, such as sodium hydroxide, potassium hydroxide, ammonia or aqueous ammonia, or acid compounds, such as phosphoric acid or sulfuric acid, can be employed in a suitable manner to control the pH of the culture. Antifoams, such as e.g. fatty acid polyglycol esters, can be employed to control the development of foam. Suitable substances having a selective action, such as e.g. antibiotics, can be added to the medium to maintain the stability of plasmids. To maintain aerobic conditions, oxygen or oxygen-containing gas mixtures, such as e.g. air, are introduced into the culture. The temperature of the culture is usually 20° C. to 45° C., and preferably 25° C. to 40° C. Culturing is continued until a maximum of the desired product has formed. This target is usually reached within 10 hours to 160 hours.

The fermentation broths obtained in this way, in particular containing L-methionine, usually have a dry weight of 7.5 to 25 wt. % and contain L-methionine. It is also advantageous if the fermentation is conducted in a sugar-limited procedure at least at the end, but in particular over at least 30% of the duration of the fermentation. That is to say, the concentration of utilizable sugar in the fermentation medium is reduced to ≧0 to 3 g/l during this period.

The fermentation broth prepared in this manner, in particular containing L-methionine, is then further processed. Depending on requirements, the all or some of the biomass can be removed from the fermentation broth by separation methods, such as e.g. centrifugation, filtration, decanting or a combination thereof, or it can be left completely in this. This broth is then thickened or concentrated by known methods, such as e.g. with the aid of a rotary evaporator, thin film evaporator, falling film evaporator, by reverse osmosis, or by nanofiltration. This concentrated fermentation broth can then be worked up by methods of freeze drying, spray drying, spray granulation or by other processes to give a preferably free-flowing, finely divided powder.

This free-flowing, finely divided powder can then in turn by converted by suitable compacting or granulating processes into a coarse-grained, readily free-flowing, storable and largely dust-free product. In the granulation or compacting it is advantageous to employ conventional organic or inorganic auxiliary substances or carriers, such as starch, gelatin, cellulose derivatives or similar substances, such as are conventionally used as binders, gelling agents or thickeners in foodstuffs or feedstuffs processing, or further substances, such as, for example, silicas, silicates or stearates.

“Free-flowing” is understood as meaning powders which flow unimpeded out of the vessel with the opening of 5 mm (millimeters) of a series of glass outflow vessels with outflow openings of various sizes (Klein, Seifen, Öle, Fette, Wachse 94, 12 (1968)).

As described here, “finely divided” means a powder with a predominant content (>50%) with a particle size of 20 to 200 μm diameter. “Coarse-grained” means products with a predominant content (>50%) with a particle size of 200 to 2000 μm diameter. In this context, “dust-free” means that the product contains only small contents (<5%) with particle sizes of less than 20 μm diameter. The particle size determination can be carried out with methods of laser diffraction spectrometry. The corresponding methods are described in the textbook on “Teilchengröβenmessung in der Laborpraxis” by R. H. Müller and R. Schuhmann, Wissenschaftliche Verlagsgesellschaft Stuttgart (1996) or in the textbook “Introduction to Particle Technology” by M. Rhodes, Verlag Wiley & Sons (1998).

“Storable” in the context of this invention means a product which can be stored for up to 120 days, preferably up to 52 weeks, particularly preferably 60 months, without a substantial loss (<5%) of methionine occurring.

Alternatively, however, the product can be absorbed on to an organic or inorganic carrier substance which is known and conventional in feedstuffs processing, such as, for example, silicas, silicates, grits, brans, meals, starches, sugars or others, and/or mixed and stabilized with conventional thickeners or binders. Use examples and processes in this context are described in the literature (Die Mühle+Mischfuttertechnik 132 (1995) 49, page 817).

Finally, the product can be brought into a state in which it is stable to digestion by animal stomachs, in particular the stomach of ruminants, by coating processes (“coating”) using film-forming agents, such as, for example, metal carbonates, silicas, silicates, alginates, stearates, starches, gums and cellulose ethers, as described in DE-C-4100920.

If the biomass is separated off during the process, further inorganic solids, for example added during the fermentation, are in general removed. In addition, the animal feedstuffs additive according to the invention comprises at least the predominant proportion of the further substances, in particular organic substances, which are formed or added and are present in solution in the fermentation broth, where these have not been separated off by suitable processes.

In one aspect of the invention, the biomass can be separated off to the extent of up to 70%, preferably up to 80%, preferably up to 90%, preferably up to 95%, and particularly preferably up to 100%. In another aspect of the invention, up to 20% of the biomass, preferably up to 15%, preferably up to 10%, preferably up to 5%, particularly preferably no biomass is separated off.

These organic substances include organic by-products which are optionally produced, in addition to the L-methionine, and optionally discharged by the microorganisms employed in the fermentation. These include L-amino acids chosen from the group consisting of L-lysine, L-valine, L-threonine, L-alanine or L-tryptophan. They include vitamins chosen from the group consisting of vitamin B1 (thiamine), vitamin B2 (riboflavin),vitamin B5 (pantothenic acid), vitamin B6 (pyridoxine), vitamin B12 (cyanocobalamin), nicotinic acid/nicotinamide and vitamin E (tocopherol). They include furthermore organic acids which carry one to three carboxyl groups, such as, for example, acetic acid, lactic acid, citric acid, malic acid or fumaric acid. Finally, they also include sugars, such as, for example, trehalose. These compounds are optionally desired if they improve the nutritional value of the product.

These organic substances, including L-methionine and/or D-methionine and/or the racemic mixture D,L-methionine, can also be added, depending on requirements, as a concentrate or pure substance in solid or liquid form during a suitable process step. These organic substances mentioned can be added individually or as mixtures to the resulting or concentrated fermentation broth, or also during the drying or granulation process. It is likewise possible to add an organic substance or a mixture of several organic substances to the fermentation broth and a further organic substance or a further mixture of several organic substances during a later process step, for example granulation.

The product described above is suitable as a feedstuffs additive, i.e. feed additive, for animal nutrition.

The L-methionine content of the animal feedstuffs additive is conventionally 1 wt. % to 80 wt. %, preferably 2 wt. % to 80 wt. %, particularly preferably 4 wt. % to 80 wt. %, and very particularly preferably 8 wt. % to 80 wt. %, based on the dry weight of the animal feedstuffs additive. Contents of 1 wt. % to 60 wt. %, 2 wt. % to 60 wt. %, 4 wt. % to 60 wt. %, 6 wt. % to 60 wt. %, 1 wt. % to 40 wt. %, 2 wt. % to 40 wt. % or 4 wt. % to 40 wt. % are likewise possible. The water content of the feedstuffs additive is conventionally up to 5 wt. %, preferably up to 4 wt. %, and particularly preferably less than 2 wt. %.

The invention accordingly also provides a process for the preparation of an L-methionine-containing animal feedstuffs additive from fermentation broths, which comprises the steps

-   -   (a) culture and fermentation of an L-methionine-producing         microorganism in a fermentation medium;     -   (b) removal of water from the L-methionine-containing         fermentation broth (concentration);     -   (c) removal of an amount of 0 to 100 wt. % of the biomass formed         during the fermentation; and     -   (d) drying of the fermentation broth obtained according to a)         and/or b) to obtain the animal feedstuffs additive in the         desired powder or granule form.

If desired, one or more of the following steps can furthermore be carried out in the process according to the invention:

-   -   (e) addition of one or more organic substances, including         L-methionine and/or D-methionine and/or the racemic mixture         D,L-methionine, to the products obtained according to a), b)         and/or c);     -   (f) addition of auxiliary substances chosen from the group         consisting of silicas, silicates, stearates, grits and bran to         the substances obtained according to a) to d) for stabilization         and to increase the storability; or     -   (g) conversion of the substances obtained according to a) to e)         into a form which is stable in an animal stomach, in particular         rumen, by coating with film-forming agents.

Methods for the determination of L-amino acids are known from the literature. The analysis can thus be carried out, for example, as described by Spackman et al. (Analytical Chemistry, 30, (1958), 1190) by ion exchange chromatography with subsequent ninhydrin derivation, or it can be carried out by reversed phase HPLC, for example as described by Lindroth et al. (Analytical Chemistry (1979) 51: 1167-1174).

The process according to the invention is used for fermentative preparation of amino acids.

The following microorganisms were deposited as a pure culture on 18 May 2001 at the Deutsche Sammlung fur Mikroorganismen und Zellkulturen (DSMZ=German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany) in accordance with the Budapest Treaty:

-   -   E. coli DH5αmcr/pEC-XK99EcysEb1ex as DSM 14308,     -   E. coli DH5αmcr/pEC-XK99EcysKa1ex as DSM 14310,     -   E. coli DH5αmcr/pEC-XK99EcysDa1ex as DSM 14311,     -   E. coli DH5αmcr/pEC-XK99EcysHa1ex as DSM 14315.

EXAMPLES

Having generally described this invention, a further understanding can be obtained by reference to certain specific examples which are provided herein for purposes of illustration only and are not intended to be limiting unless otherwise specified.

The isolation of plasmid DNA from Escherichia coli and all techniques of restriction, Klenow and alkaline phosphatase treatment were carried out by the method of Sambrook et al. (Molecular Cloning. A Laboratory Manual (1989) Cold Spring Harbour Laboratory Press, Cold Spring Harbor, N.Y., USA). Methods for transformation of Escherichia coli are also described in this handbook.

The composition of the usual nutrient media, such as LB or TY medium, can also be found in the handbook by Sambrook et al.

Example 1 Preparation of a Genomic Cosmid Gene Library From Corynebacterium Glutamicum ATCC 13032

Chromosomal DNA from Corynebacterium glutamicum ATCC 13032 was isolated as described by Tauch et al. (1995, Plasmid 33:168-179) and partly cleaved with the restriction enzyme Sau3AI (Amersham Pharmacia, Freiburg, Germany, Product Description Sau3AI, Code no. 27-0913-02). The DNA fragments were dephosphorylated with shrimp alkaline phosphatase (Roche Diagnostics GmbH, Mannheim, Germany, Product Description SAP, Code no. 1758250). The DNA of the cosmid vector SuperCos1 (Wahl et al. (1987) Proceedings of the National Academy of Sciences USA 84:2160-2164), obtained from Stratagene (La Jolla, USA, Product Description SuperCos1 Cosmid Vector Kit, Code no. 251301) was cleaved with the restriction enzyme XbaI (Amersham Pharmacia, Freiburg, Germany, Product Description XbaI, Code no. 27-0948-02) and likewise dephosphorylated with shrimp alkaline phosphatase.

The cosmid DNA was then cleaved with the restriction enzyme BamHI (Amersham Pharmacia, Freiburg, Germany, Product Description BamHI, Code no. 27-0868-04). The cosmid DNA treated in this manner was mixed with the treated ATCC13032 DNA and the batch was treated with T4 DNA ligase (Amersham Pharmacia, Freiburg, Germany, Product Description T4-DNA-Ligase, Code no.27-0870-04). The ligation mixture was then packed in phages with the aid of Gigapack II XL Packing Extract (Stratagene, La Jolla, USA, Product Description Gigapack II XL Packing Extract, Code no. 200217).

For infection of the E. coli strain NM554 (Raleigh et al. 1988, Nucleic Acid Research 16:1563-1575) the cells were taken up in 10 mM MgSO₄ and mixed with an aliquot of the phage suspension. The infection and titering of the cosmid library were carried out as described by Sambrook et al. (1989, Molecular Cloning: A laboratory Manual, Cold Spring Harbor), the cells being plated out on LB agar (Lennox, 1955, Virology, 1:190) with 100 mg/l ampicillin. After incubation overnight at 37° C., recombinant individual clones were selected.

Example 2 Isolation and Sequencing of the cysD Gene, the cysN Gene, the cysK Gene, the cysE Gene or the cysH Gene

The cosmid DNA of an individual colony was isolated with the Qiaprep Spin Miniprep Kit (Product No. 27106, Qiagen, Hilden, Germany) in accordance with the manufacturer's instructions and partly cleaved with the restriction enzyme Sau3AI (Amersham Pharmacia, Freiburg, Germany, Product Description Sau3AI, Product No. 27-0913-02). The DNA fragments were dephosphorylated with shrimp alkaline phosphatase (Roche Diagnostics GmbH, Mannheim, Germany, Product Description SAP, Product No. 1758250). After separation by gel electrophoresis, the cosmid fragments in the size range of 1500 to 2000 bp were isolated with the QiaExII Gel Extraction Kit (Product No. 20021, Qiagen, Hilden, Germany).

The DNA of the sequencing vector pZero-1, obtained from Invitrogen (Groningen, Holland, Product Description Zero Background Cloning Kit, Product No. K2500-01), was cleaved with the restriction enzyme BamHI (Amersham Pharmacia, Freiburg, Germany, Product Description BamHI, Product No. 27-0868-04). The ligation of the cosmid fragments in the sequencing vector pZero-1 was carried out as described by Sambrook et al. (1989, Molecular Cloning: A Laboratory Manual, Cold Spring Harbor), the DNA mixture being incubated overnight with T4 ligase (Pharmacia Biotech, Freiburg, Germany). This ligation mixture was then electroporated (Tauch et al. 1994, FEMS Microbiol Letters, 123:343-7) into the E. coli strain DH5αMCR (Grant, 1990, Proceedings of the National Academy of Sciences U.S.A., 87:4645-4649) and plated out on LB agar (Lennox, 1955, Virology, 1:190) with 50 mg/l zeocin.

The plasmid preparation of the recombinant clones was carried out with the Biorobot 9600 (Product No. 900200, Qiagen, Hilden, Germany). The sequencing was carried out by the dideoxy chain termination method of Sanger et al. (1977, Proceedings of the National Academy of Sciences U.S.A., 74:5463-5467) with modifications according to Zimmermann et al. (1990, Nucleic Acids Research, 18:1067). The “RR dRhodamin Terminator Cycle Sequencing Kit” from PE Applied Biosystems (Product No. 403044, Weiterstadt, Germany) was used. The separation by gel electrophoresis and analysis of the sequencing reaction were carried out in a “Rotiphoresis NF Acrylamide/Bisacrylamide” Gel (29: 1) (Product No. A124. 1, Roth, Karlsruhe, Germany) with the “ABI Prism 377” sequencer from PE Applied Biosystems (Weiterstadt, Germany).

The raw sequence data obtained were then processed using the Staden program package (1986, Nucleic Acids Research, 14:217-231) version 97-0. The individual sequences of the pZero1 derivatives were assembled to a continuous contig. The computer-assisted coding region analysis was prepared with the XNIP program (Staden, 1986, Nucleic Acids Research, 14:217-231).

The resulting nucleotide sequences are shown in SEQ ID No. 1 SEQ ID No. 4 and SEQ ID No. 7. Analysis of the nucleotide sequences showed six open reading frames of 915 base pairs, 1302 base pairs, 936 base pairs, 567 base pairs and 786 base pairs, which were called the cysD gene, cysN gene, cysK gene, cysE gene and cysH gene. The cysD gene codes for a protein of 304 amino acids, the cysN gene codes for a protein of 433 amino acids, the cysK gene codes for a protein of 311 amino acids, the cysE gene codes for a protein of 188 amino acids and the cysH gene codes for a protein of 261 amino acids.

Example 3 Preparation of Shuttle Expression Vectors Based on pEC-XK99E for Enhancement of the cysD, cysK, cysE and cysH Genes in C. Glutamicum

3.1 Amplification of the cysD, cysK, cysE and cysH Genes

From the strain ATCC 13032, chromosomal DNA was isolated by the method of Eikmanns et al. (Microbiology 140: 1817-1828 (1994)). On the basis of the sequences of the cysD, cysK, cysE and cysH genes known for C. glutamicum from Example 2, the following oligonucleotides, listed in Table 1, were chosen for the polymerase chain reaction (see SEQ ID No. 9, SEQ ID No. 10, SEQ ID No. 11, SEQ ID No. 12, SEQ ID No. 13, SEQ ID No. 14, SEQ ID No. 15 and SEQ ID No. 16). In addition, suitable restriction cleavage sites which allow cloning into the target vector were inserted into the primers. They are listed in Table 1 and identified by underlining in the nucleotide sequence. TABLE 1 Primer Sequence with restriction cleavage site Amplified fragment cysDex1 5′-ctggtacc-gcggacttcactcatgacca-3′ cysD KpnI (1017 bp) cysDex2 5′-cgtctaga-ggaacctgcggtgcacagac-3′ XbaI cysKex1 5′-agggtacc-caagcggtcgaccaacaaaa-3′ cysK KpnI (1005 bp) cysKex2 5′-cttctaga-attagtcgcggatgtcttcg-3′ XbaI cysEex1 5′-ctggtacc-tcacgctgttagacttgcct-3 cysE KpnI (672 bp) cysEex2 5′-gatctaga-acaaacgcactctggagctt-3′ XbaI cysHex1 5′-acggtacc-tgagtcgcaacaatgagctt-3′ cysH KpnI (884 bp) cysHex2 5′-gttctaga-cggaggatgtggatggattc-3′ XbaI

The primers shown were synthesized by MWG-Biotech AG (Ebersberg, Germany) and the PCR reaction was carried out by the standard PCR method of Innis et al. (PCR Protocols. A Guide to Methods and Applications, 1990, Academic Press) with Pwo-Polymerase from Roche Diagnostics GmbH (Mannheim, Germany). With the aid of the polymerase chain reaction, the primers allow amplification of a DNA fragment 1017 bp in size, which carries the cysD gene, and a DNA fragment 1005 bp in size, which carries the cysK gene, a DNA fragment 672 bp in size, which carries the cysE gene, and a DNA fragment 884 bp in size, which carries the cysH gene.

The cysD fragment, the cysK fragment, the cysE fragment and the cysH fragment were cleaved with the restriction endonucleases KpnI and XbaI and then isolated from the agarose gel with the QiaExII Gel Extraction Kit (Product No. 20021, Qiagen, Hilden, Germany).

3.2 Construction of the Shuttle Vector pEC-XK99E

The E. coli-C. glutamicum shuttle vector pEC-XK99E was constructed according to techniques well-known to those skilled in the art. The vector contains the replication region rep of the plasmid pGA1 including the replication effector per (U.S. Pat. No. 5,175,108; Nesvera et al., Journal of Bacteriology 179, 1525-1532 (1997)), the kanamycin resistance gene aph(3′)-IIa from Escherichia coli (Beck et al. (1982), Gene 19: 327-336), the replication origin of the trc promoter, the termination regions T1 and T2, the lacI^(q) gene (repressor of the lac operon of E. coli) and a multiple cloning site (mcs) (Norrander, J. M. et al. Gene 26, 101-106 (1983)) of the plasmid pTRC99A (Amann et al. (1988), Gene 69: 301-315).

The E. coli-C. glutamicum shuttle vector pEC-XK99E constructed was transferred into C. glutamicum DSM5715 by means of electroporation (Liebl et al., 1989, FEMS Microbiology Letters, 53:299-303). Selection of the transformants took place on LBHIS agar comprising 18.5 g/l brain-heart infusion broth, 0.5 M sorbitol, 5 g/l Bacto-tryptone, 2.5 g/l Bacto-yeast extract, 5 g/l NaCl and 18 g/l Bacto-agar, which had been supplemented with 25 mg/l kanamycin. Incubation was carried out for 2 days at 33° C.

Plasmid DNA was isolated from a transformant by conventional methods (Peters-Wendisch et al., 1998, Microbiology, 144, 915-927), cleaved with the restriction endonuclease HindIII, and the plasmid was checked by subsequent agarose gel electrophoresis.

The plasmid construct thus obtained in this way was called pEC-XK99E and is shown in FIG. 1. The strain obtained by electroporation of the plasmid pEC-XK99E in the C. glutamicum strain DSM5715 was called DSM5715/pEC-XK99E and deposited as DSM 13455 at the Deutsche Sammlung für Mikroorganismen und Zellkulturen (DSMZ=German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany) in accordance with the Budapest Treaty.

3.3 Cloning of the cysD, cysK, cysE and cysH Genes in the E. coli-C. Glutamicum Shuttle Vector pEC-XK99E

The E. coli-C. glutamicum shuttle vector pEC-XK99E described in Example 3.1 was used as the vector. DNA of this plasmid was cleaved completely with the restriction enzymes KpnI and XbaI and then dephosphorylated with shrimp alkaline phosphatase (Roche Diagnostics GmbH, Mannheim, Germany, Product Description SAP, Product No. 1758250).

The fragments cysD, approx. 1000 bp in size, cysK, approx. 990 bp in size, cysE, approx. 660 bp in size and cysH, approx. 870 bp in size cleaved with the restriction enzymes KpnI and XbaI and isolated from the agarose gel were in each case mixed with the prepared vector pEC-XK99E and the batches were treated with T4 DNA ligase (Amersham Pharmacia, Freiburg, Germany, Product Description T4-DNA-Ligase, Code no.27-0870-04). The ligation batches were transformed in the E. coli strain DH5αmcr (Hanahan, In: DNA Cloning. A Practical Approach. Vol. I, IRL-Press, Oxford, Washington D.C., USA). Selection of plasmid-carrying cells was made by plating out the transformation batches on LB agar (Lennox, 1955, Virology, 1:190) with 50 mg/l kanamycin. After incubation overnight at 37° C., recombinant individual clones were selected. Plasmid DNA was isolated from a transformant in each case with the Qiaprep Spin Miniprep Kit (Product No. 27106, Qiagen, Hilden, Germany) in accordance with the manufacturer's instructions and cleaved with the restriction enzymes KpnI and XbaI to check the plasmid by subsequent agarose gel electrophoresis. The plasmids obtained were called pEC-XK99EcysDa1ex, pEC-XK99EcysKa1ex, pEC-XK99EcysEb1ex and pEC-XK99EcysHa1ex. They are shown in FIGS. 2, 3, 4 and 5.

Example 4

Transformation of the Strain DSM5715 with the Plasmids pEC-XK99EcysDa1ex, pEC-XK99EcysKa1ex, pEC-XK99EcysEb1ex and pEC-XK99EcysHa1ex The strain DSM5715 was transformed with in each case one of the plasmids pEC-XK99EcysDa1ex, pEC-XK99EcysKa 1 ex, pEC-XK99EcysEb1ex and pEC-XK99EcysHa1ex using the electroporation method described by Liebl et al., (FEMS Microbiology Letters, 53:299-303 (1989)). Selection of the transformants took place on LBHIS agar comprising 18.5 g/l brain-heart infusion broth, 0.5 M sorbitol, 5 g/l Bacto-tryptone, 2.5 g/l Bacto-yeast extract, 5 g/l NaCl and 18 g/l Bacto-agar, which had been supplemented with 25 mg/l kanamycin. Incubation was carried out for 2 days at 33° C.

Plasmid DNA was isolated from a transformant in each case by conventional methods (Peters-Wendisch et al., 1998, Microbiology 144, 915-927). DNA of the plasmids pEC-XK99EcysDa1ex, pEC-XK99EcysKa1ex, pEC-XK99EcysEb1ex and pEC-XK99EcysHa1ex were cleaved with the restriction endonucleases KpnI and XbaI. The plasmids were checked by subsequent agarose gel electrophoresis. The strains obtained were called DSM5715/pEC-XK99EcysDa1ex, DSM5715/pEC-XK99EcysKa1ex, DSM5715/pEC-XK99EcysEb1ex or DSM5715/pEC-XK99EcysHa1ex.

Example 5 Preparation of Lysine

The C. glutamicum strains DSM5715/pEC-XK99EcysDa1ex, DSM5715/pEC-XK99EcysKa1ex, DSM5715/pEC-XK99EcysEb1ex or DSM5715/pEC-XK99EcysHa1ex obtained in Example 4 were cultured in a nutrient medium suitable for the production of lysine and the lysine content in the culture supernatant of each strain was determined.

For this, the strains were first incubated on an agar plate with the corresponding antibiotic (brain-heart agar with kanamycin (25 mg/l)) for 24 hours at 33° C. Starting from this agar plate culture, in each case a preculture was seeded (10 ml medium in a 100 ml conical flask). The complete medium CgIII was used as the medium for the precultures. Medium Cg III NaCl 2.5 g/l Bacto-Peptone 10 g/l Bacto-Yeast extract 10 g/l Glucose (autoclaved separately) 2% (w/v) The pH was brought to pH 7.4

Kanamycin (25 mg/l) was added to this. The precultures were incubated for 16 hours at 33° C. at 240 rpm on a shaking machine. In each case a main culture was seeded from these precultures such that the initial OD (660 nm) of the main cultures was 0.1. Medium MM was used for the main cultures. Medium MM CSL (corn steep liquor) 5 g/l MOPS (morpholinopropanesulfonic acid) 20 g/l Glucose (autoclaved separately) 50 g/l (NH₄)₂SO₄ 25 g/l KH₂PO₄ 0.1 g/l MgSO₄ * 7 H₂O 1.0 g/l CaCl₂ * 2 H₂O 10 mg/l FeSO₄ * 7 H₂O 10 mg/l MnSO₄ * H₂O 5.0 mg/l Biotin (sterile-filtered) 0.3 mg/l Thiamine * HCl (sterile-filtered) 0.2 mg/l L-Leucine (sterile-filtered) 0.1 g/l CaCO₃ 25 g/l

The CSL, MOPS and the salt solution were brought to pH 7 with aqueous ammonia and autoclaved. The sterile substrate and vitamin solutions were then added, as well as the CaCO₃ autoclaved in the dry state.

Culturing was carried out in a 10 ml volume in a 100 ml conical flask with baffles. Kanamycin (25 mg/l) was added. Culturing was carried out at 33° C. and 80% atmospheric humidity.

After 48 hours the OD of the cultures DSM5715, DSM5715/pEC-XK99EcysDa1ex, DSM5715/pEC-XK99EcysKa1ex and DSM5715/pEC-XK99EcysHa1ex and after 72 hours the OD of the culture DSM5715/pEC-XK99EcysEb1ex was determined at a measurement wavelength of 660 nm with a Biomek 1000 (Beckmann Instruments GmbH, Munich). The amount of lysine formed was in each case determined with an amino acid analyzer from Eppendorf-BioTronik (Hamburg, Germany) by ion exchange chromatography and post-column derivation with ninhydrin detection.

The result of the experiment is shown in Tables 2 and 3. TABLE 2 Lysine HCl Strain OD (660 nm) (48 h) g/l (48 h) DSM5715 11.3 13.11 DSM5715/pEC- 13.7 13.54 XK99EcysDa1ex DSM5715/pEC- 13.5 14.35 XK99EcysKa1ex DSM5715/pEC- 11.5 15.22 XK99EcysHa1ex

TABLE 3 Lysine HCl Strain OD (660 nm) (72 h) (72 h)g/l DSM5715 7.17 14.27 DSM5715/pEC- 9.0 15.22 XK99EcysEb1ex

Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

The publications cited above are incorporated herein by reference.

This application is based on German Patent Application Serial Nos. 100 48 603.7, filed on Sep. 30, 2000, 101 09 691.7, filed on Feb. 28, 2001, and 101 36 986.7, filed on Jul. 28, 2001, each of which is incorporated herein by reference. 

1-20. (canceled)
 21. A modified coryneform bacterium in which at least one of the cysD gene, cysN gene, cysK gene, cysE gene and the cysH gene are enhanced relative to an unmodified coryneform bacterium.
 22. The modified coryneform bacterium of claim 21, wherein at least one of cysD gene, cysN gene, cysK gene, cysE gene and the cysH gene are over-expressed.
 23. Microorganism DSM 14308 deposited at the Deutsche Sammlung für Mikroorganismen und Zellkulturen.
 24. Escherichia coli strain DH5αmcr/pEC-XK99EcysKa1ex deposited as DSM 14310 deposited at the Deutsche Sammlung für Mikroorganismen und Zellkulturen.
 25. Escherichia coli strain DH5αmcr/pEC-XK99EcysDa1ex deposited as DSM 14311 deposited at the Deutsche Sammlung für Mikroorganismen und Zelikulturen.
 26. Escherichia coli strain DH5αmcr/pEC-XK99EcysHa1ex as DSM 14315 deposited at the Deutsche Sammlung für Mikroorganismen und Zellkulturen.
 27. A process for the fermentative preparation of an L-amino acid comprising: (a) fermenting the modified coryneform bacterium of claim 21 in a medium wherein the modified coryneform bacterium produce the L-amino acid (b) concentrating the L-amino acid in the medium or in the cells of the bacteria, and (c) isolating the L-amino acid.
 28. The process of claim 27, wherein the amino acid is L-lysine.
 29. The process of claim 27, wherein the L-amino acid is L-cysteine or L-methionine. 30-31. (canceled)
 32. The process of claim 27, wherein the bacteria are transformed with a plasmid vector, and the plasmid vector comprises at least one polynucleotide which encodes a gene product selected from the group consisting of cysD, cysN, cysK, cysE and cysH. 33-35. (canceled)
 36. The process of claim 27, wherein the modified coryneform bacterium further comprises at least one gene whose expression is enhanced, wherein the at least one gene is selected from the group consisting of the dapA gene which codes for dihydrodipicolinate synthase, the gap gene which codes for glyceraldehyde 3-phosphate dehydrogenase, the tpi gene which codes for triose phosphate isomerase, the pgk gene which codes for 3-phosphoglycerate kinase, the zwf gene which codes for glucose 6-phosphate dehydrogenase, the pyc gene which codes for pyruvate carboxylase, the mqo gene which codes for malate-quinone oxidoreductase, the lysC gene which codes for a feed-back resistant aspartate kinase, the lysE gene which codes for lysine export, the hom gene which codes for homoserine dehydrogenase, the ilvA gene which codes for threonine dehydratase, the ilvA(Fbr) allele which codes for a feed back resistant threonine dehydratase, the ilvBN gene which codes for acetohydroxy-acid synthase, the ilvD gene which codes for dihydroxy-acid dehydratase, and the zwa1 gene which codes for the Zwa1 protein.
 37. The process of claim 27, wherein the modified coryneform bacterium further comprises at least one gene whose expression is attenuated, wherein the at least one gene is selected from the group consisting of the pck gene which codes for phosphoenol pyruvate carboxykinase, the pgi gene which codes for glucose 6-phosphate isomerase, the poxB gene which codes for pyruvate oxidase, and the zwa2 gene which codes for the Zwa2 protein.
 38. The process of claim 27, wherein the modified coryneform bacterium further comprises at least one gene whose expression is attenuated, wherein the at least one gene is selected from the group consisting of the aecD gene which codes for cystathionine β-lyase, and the metB gene which codes for cystathionine synthase.
 39. The process of claim 27, wherein the modified coryneform bacterium is Corynebacterium glutamicum.
 40. The process of claim 39, wherein the Corynebacterium glutamicum is strain DSM5715/pEC-XK99EcysDa1ex.
 41. The process of claim 39, wherein the Corynebacterium glutamicum is strain DSM5715/pEC-XK99EcysKa1ex.
 42. The process of claim 39, wherein the Corynebacterium glutamicum is strain DSM5715/pEC-XK99EcysEb1ex.
 43. The process of claim 39, wherein the Corynebacterium glutamicum is strain DSM5715/pEC-XK99EcysHa1ex.
 44. (canceled)
 45. A process of the preparation of an L-methionine-containing animal feedstuffs additive from a fermentation broth, comprising: (a) culturing and fermenting an L-methionine-producing microorganism in a fermentation medium; (b) removing water from the L-methionine-containing fermentation broth; (c) removing an amount of from 0 to 100 wt. % of the biomass formed during the fermentation; and (d) drying the fermentation broth obtained according to (b) and/or (c) to obtain the animal feedstuffs additive in powder or granule form.
 46. The process of claim 45, wherein genes in the biosynthesis pathway of L-methionine are enhanced.
 47. The process of claim 45, wherein the metabolic pathways which reduce the formation of L-methionine are at least partly eliminated in the microorganism.
 48. The process of claim 45, wherein the expression of the polynucleotides which code for cysD, cysN, cysK, cysE or cysH is enhanced in the microorganism.
 49. The process of claim 45, wherein the expression of the polynucleotides which code for cysD, cysN, cysK, cysE or cysH is over-expressed in the microorganism.
 50. The process of claim 45, wherein microorganism is Corynebacterium glutamicum.
 51. The process of claim 50, wherein the Corynebacterium glutamicum strain is DSM5715/pEC-XK99EcysDa1ex.
 52. The process of claim 50, wherein the Corynebacterium glutamicum is strain DSM5 715/pEC-XK99EcysKa1ex.
 53. The process of claim 50, wherein the Corynebacterium glutamicum is strain DSM5715/pEC-XK99EcysEb1ex.
 54. The process according to claim 50, wherein the Corynebacterium glutamicum strain is DSM5715/pEC-XK99EcysHa1ex.
 55. The process of claim 45, further comprising one or more of the following steps: e) adding one or more organic substances to the products obtained according to b), c) and/or d); f) adding auxiliary substances selected from the group consisting of silicas, silicates, stearates, grits, and bran to the substances obtained according to (b) to (e) for stabilization and to increase the storability; or g) converting the substances obtained according to (b) to (f) into a form which is stable in an animal stomach by coating with film-forming agents.
 56. The process of claim 55, which comprises step (e) and wherein the said organic substances are selected from the group consisting of L-methionine, D-methionine, a racemic mixture D,L-methionine, and combinations thereof.
 57. The process of claim 45, wherein some of the biomass is removed.
 58. The process of claim 55, wherein some of the biomass is removed.
 59. The process of claim 45, wherein up to 100% of the biomass is removed.
 60. The process of claim 55, wherein up to 100% of the biomass is removed.
 61. The process of claim 45, wherein the water content is up to 5 wt. %.
 62. The process of claim 55, wherein the water content is up to 5 wt. %.
 63. The process of claim 50, wherein the water content is less than 2 wt. %.
 64. The process of claim 45, wherein the water content is less than 2 wt. %.
 65. The process of claim 55, wherein the water content is less than 2 wt. %.
 66. The process of claim 55, wherein the film-forming agents are metal carbonates, silicas, silicates, alginates, stearates, starches, gums or cellulose ethers.
 67. An animal feedstuff additive prepared according to claim
 45. 68. The animal feedstuff additive of claim 67, which comprises 1 wt. % to 80 wt. % L-methionine, D-methionine, D,L-methionine or a mixture thereof, based on the dry weight of the animal feedstuffs additive. 69-70. (canceled)
 71. The modified coryneform bacterium of claim 21, wherein the cysD gene is enhanced and wherein the cysD gene codes for a polypeptide which comprises the amino acid sequence of SEQ ID No. 2, the cysD gene comprises nucleotides 232 to 1143 of SEQ ID No. 1, or at least one sequence which hybridizes with the sequence fully complementary to sequence nucleotides 232 to 1143 of SEQ ID No. 1, wherein the hybridization conditions comprise washing in 2×SSC at a temperature of from 50 to 68° C. and which encodes a polypeptide with sulfate adenylyltransferase activity.
 72. The modified coryneform bacterium of claim 21, wherein the cysN gene is enhanced and wherein the cysN gene codes for a polypeptide which comprises the amino acid sequence of SEQ ID No. 3, the cysN gene comprises nucleotides 1146 to 2444 of SEQ ID No. 1, or at least one sequence which hybridizes with the sequence fully complementary to sequence nucleotides 1146 to 2444 of SEQ ID No. 1, wherein the hybridization conditions comprise washing in 2×SSC at a temperature of from 50 to 68° C. and which encodes a polypeptide with sulfate adenylyltransferase activity.
 73. The modified coryneform bacterium of claim 21, wherein the cysK gene is enhanced and wherein the cysK gene codes for a polypeptide which comprises the amino acid sequence of SEQ ID No. 5, the cysK gene comprises nucleotides 271 to 1203 of SEQ ID No. 4, or at least one sequence which hybridizes with the sequence fully complementary to sequence nucleotides 271 to 1203 of SEQ ID No. 4, wherein the hybridization conditions comprise washing in 2×SSC at a temperature of from 50 to 68° C. and which encodes a polypeptide with cysteine synthase A activity.
 74. The modified coryneform bacterium of claim 21, wherein the cysE gene is enhanced and wherein the cysE gene codes for a polypeptide which comprises the amino acid sequence of SEQ ID No. 6, the cysE gene comprises nucleotides 1392 to 1955 of SEQ ID No.4, or at least one sequence which hybridizes with the sequence fully complementary to sequence nucleotides 1392 to 1955 of SEQ ID No.4, wherein the hybridization conditions comprise washing in 2×SSC at a temperature of from 50 to 68° C. and which encodes a polypeptide with serine acetyltransferase activity.
 75. The modified coryneform bacterium of claim 21, wherein the cysH gene is enhanced and wherein the cysH gene codes for a polypeptide which comprises the amino acid sequence of SEQ ID No. 8, the cysH gene comprises nucleotides 250 to 1032 of SEQ ID No. 7, or at least one sequence which hybridizes with the sequence fully complementary to sequence nucleotides 250 to 1032 of SEQ ID No. 7, wherein the hybridization conditions comprise washing in 2×SSC at a temperature of from 50 to 68° C. and which encodes a polypeptide with 3′-phopshoadenylyl sulfate reductase activity. 